Dredges are commonly used to remove sediments from the bottom of various bodies of water. This can involve everything from dredging sand from a river bottom to removing sludge from sludge pits.
Dredges typically have a hull which floats on top of the water. A boom with a cutter head is pivotally attached to the hull. When it is in the lowered position, the cutter head can be operated in combination with a pump to remove a slurry of material from the bottom of the body of water.
The operation of the cutter head requires a significant amount of force to stir and agitate the material on the bottom. Thus traditionally dredges have been located and moved using a set of cables spanning the body of water being dredged. The dredge traverses the body of water either by taking in and paying out cable using winches mounted on the dredge or by traveling along a single cable with a winch mounted on the dredge. Thus the dredge is limited in its scope of operation to a path of traversing the cables. In order to dredge additional areas the anchors on the end of the cables must be moved so that the dredge can traverse a new swath or path of area across the body of water. As one can imagine relocating a dredge in this manner can be very time consuming.
In addition to the time consuming nature of moving such a dredge, the cables also present a hazard to nearby boats and vessels. If the cables are overhead, they can severely limit the height of vessels able to operate adjacent to the dredge. Similarly if the cables are anchored underwater they present an unseen hazard to the other vessels operating in the area. This greatly reduces the depth of draft a vessel can have and safely operate in the area.
Other parties have seen the shortcomings of navigating dredges using such a cable system and have resorted to use of paddle wheels, however the paddle wheels only work when they are on the surface of the water or engaged with the bottom of the body of water. Dredges using paddle wheels will not work when the paddle wheels are not in either of these locations.
Further the paddle wheels are located on their own individual booms which can be raised and lowered. This is in addition to the boom to which the cutter head is mounted. During operation the forces exerted by the cutter head as well as those exerted by the paddle wheels must operate from the long lever arm created by the booms to which they are attached. This makes it very difficult to control the position of the dredge and often times the dredges equipped with such paddle wheels are operated with a cable and winch system in addition to the paddle wheels.
The dredge industry has thus had a long felt need for a propulsion system which can maneuver a dredge and also hold it in place while in operation. Further what is needed is a dredge propulsion system which can be quickly and easily used to maneuver about the body of water being dredged without having to relocate cables and anchors.
Additionally what is needed is a dredge propulsion system which does not present underwater and overhead hazards to surrounding vessels.